It is a known natural phenomenon that a thin boundary layer of high velocity builds up on a moving solid surface such as a gyro rotor. A technique for sensing this boundary layer around a gyro rotor has recently been developed using a scoop type probe to sense pressures, or pressure differential, in the layer. This gyro output measurement technique has demonstrated good response to offset detection, but is quite noisy due to air turbulence through the scoop. A different type of gyro offset detection is offered here which has several salient advantages in features over the scoop probes.
For several years, the heated sensor technique for fluid flow measurement has advanced steadily. This technique for fluid flow measurement employs the principle of the hot sensor anemometer, which instantaneously measures fluid-flow parameters by sensing the heat transfer between an electrically heated sensor and the flow medium.
The hot-wire anemometer is distinguished by several salient features that offer advantages over other types of flow measurement probes.
a. The device has a very quick and wide frequency response to changes in gas velocities and is the best practical means for accurately measuring the rapid fluctuations caused by turbulence, eddies, and gusts.
b. Its small size offers high spatial resolution and low interference to fluid flow. Sensor diameters are typically 0.0001" to 0.1".
c. It has excellent sensitivity which can repeatedly detect air velocities to one foot per minute.
d. It has excellent system reliability since there are no moving parts.
e. Compatibility with external signal-processing and data-gathering systems is excellent with high-level signal outputs of 0 to 10 volts.
f. Self-compensation for ambient temperature changes can be obtained with appropriate circuit.
g. The signal output for either linearized or nonlinearized anemometer output can be scaled in direct mass flow units (lbs/min, or SCFM) and required no pressure correction.
h. The system accuracy is repeatable to 0.1% of reading with obtainable resolution of 0.01% of full scale. Calibration accuracy is typically 2% of reading .+-.0.02% of full scale over a 100 to 1 flow range.